There is no all-purpose home filter. Each filtration method removes a specific class of contaminant and ignores the rest, so the way to choose is to name the problem first and then pick the method that addresses it. Here is what each of the main household technologies does, in plain terms.
Mechanical and adsorptive: sediment and carbon
Sediment filtration is a sieve: it catches sand, rust flakes and scale by size and does nothing about anything dissolved. Activated carbon works by adsorption, holding chlorine, chloramine with the right media, taste and odor compounds and many organic chemicals on an enormous internal surface area. Carbon is the workhorse of taste improvement and is nearly always present in a system, but it is finite, so a cartridge left past its capacity quietly stops working long before it looks used.
Ion exchange: softening and selective resins
Ion exchange swaps unwanted ions on a resin bed for harmless ones. A softener exchanges calcium and magnesium for sodium or potassium and regenerates with brine, which fixes scaling and soap curd but not health contaminants. Selective resins do the same trick for specific targets such as nitrate or tannins. Deionizing resin strips essentially all ions and is used where very low mineral content matters. The common thread is that ion exchange addresses charged species only.
Membranes, ultraviolet and distillation
Reverse osmosis pushes water through a semi-permeable membrane and rejects a broad range of dissolved contaminants including many that nothing else at home touches, at the cost of a drain stream and a slow fill. Ultraviolet inactivates bacteria and viruses but removes nothing chemical and needs clear water to work. Distillation boils and condenses, leaving dissolved minerals behind in the boiler. Reverse osmosis and distillation overlap heavily; the difference is throughput, energy and convenience.
Choosing by contaminant, not by brand
PFAS are a good example of matching method to problem: the EPA's 2024 rule set maximum contaminant levels of 4.0 parts per trillion for PFOA and PFOS and 10 parts per trillion for PFHxS, PFNA and GenX, while May 2026 proposals would keep the PFOA and PFOS limits with a compliance option to 2031 and rescind the others. Whatever the final position, the household answer is a certified carbon or reverse osmosis product, not a general purpose filter. Our well water testing guide covers finding out what you have.
Questions people ask about water filtration methods
Which filtration method removes the most?
Reverse osmosis and distillation remove the broadest range of dissolved contaminants, though both are slow point-of-use methods rather than whole-house ones.
Do I need more than one filtration method?
Usually yes. Systems are staged so sediment protects carbon, carbon protects a membrane, and each stage handles what the one before it cannot.
Does any filter remove bacteria?
Ultraviolet treatment, absolute-rated membranes and reverse osmosis address microbiological risk. Standard carbon and sediment cartridges do not.
Is a whole-house filter better than an under-sink one?
They do different jobs. Whole-house protects plumbing and every fixture; under-sink puts stronger treatment on the water you actually drink.